Papers by Keyword: Surface Free Energy

Abstract: PEEK is a thermoplastic polymer widely employed in the orthopedic field for the fabrication of prosthetic devices, owing to its Young’s modulus being comparable to that of cortical human bone. Surface functionalization through biomaterial micropatterning represents an effective strategy to enhance osteointegration. To this end, an innovative vibration-assisted surface embossing process was applied to PEEK samples. The surface patterning was performed using a square punch with a side length of 0.5 [mm], fabricated via CNC milling. The process is enabled by a linear actuator capable of generating controlled vibrations to induce localized sub-Tg heating of the polymer surface. After that, the application of a post-load is required for the embossing stage. This system allows frequency tuning in the range of 1–4 [kHz]. Finally, the patterned surfaces were sonicated through an ultrasound cleaner and characterized through contact angle measurements and white-light interferometry, confirming the feasibility of the process and demonstrating an increase in both the polar component of the surface free energy and the hydrophilicity compared with merely polished specimens. Enhancing the polar component of surface free energy is an effective strategy to improve biomaterial biocompatibility, confirming the relevance of the proposed surface modifications. Slightly hydrophilic surfaces promote preferential osteoblast adhesion and stable cytoskeletal organization, demonstrating the complementary roles of surface topography in shaping cellular responses.

Abstract: The paper develops a predictive model to determine the influence of the value of the dispersion component of the free surface energy (FSE) and the volume fraction of fillers on the dispersion component of the FSE of a polymer composite. Mathematical equations and graphical relationships illustrating these relationships are presented. The model is based on the assumption that in composites the FSE value is partially determined by interactions at the polymer-filler interface. Using the predictive model, it was established that the dispersion component of the free surface energy (FSE) can be a reflection of the properties of polymer composites. The reliability of the predictive assessment is shown on the example of an epoxy polymer composite with various mineral fillers.

Abstract: This research work instrumentalizes comprehensively the impacts of independent parameters like surface pressure, external magnetic field, and temperature on statistical thermodynamic quantities free energy, magnetization, occupied surface fraction, and equilibrium length. We approached it differently from a theoretical investigation conducted dealt with the behavioral dependence of surface parameters. Our mechanism was to investigate the interrelation between two dependent variables under exposure to two or more different independent parameters. Thus it seems complicated but it is used to probe surface information from the system at the same pace. We investigated the thermal excitation effect that leads to the detachment of the electron gas in contact with each occupied surface site, which reduces the adsorption of the surface in contrary external magnetic fields and pressure enhances the occupied surface probability of electrons to contact surface sites. Our findings reveal that the solid GaAs surface tends to capture electrons under the influences of external magnetic fields and pressure thus binding electrons and putting additional confining potential meanwhile the surface properties are affected. On the other hand surface, free energy has an inverse relation with magnetization, occupied surface fraction, in the case of equilibrium length it depended on the strong external magnetic fields.

Abstract: In this work we studied the effect of surface treatment of PET films, which are widely used in food packaging, on the adhesion value of ink layers based on polyvinyl chloride. To give high barrier properties to packaging laminates, the films used in their structure are coated with a nanolayer of aluminum oxide (AlOx). However, these films have a disadvantage associated with the low adhesion of adhesive and ink layers to the AlOx nanolayer. To eliminate this disadvantage, aluminium oxide nanolayer is additionally coated with various polymer coatings. In this work we studied the effect of a polyacrylic coating applied on top of an AlOx layer on improving the adhesion of ink layers. For PET films used in food packaging, optical and surface properties are also important. In this regard, additionally we measured surface free energy, coefficient of friction, and optical properties of the studied PET films. We also highlight the relationship of contact angles of wetting and the work of adhesion for the printing ink with the measured adhesion of ink layers.

Abstract: Trench-filling epitaxial growth of 4H-SiC by chemical vapor deposition (CVD) with and without HCl was analyzed based on a continuum-diffusion model including the Gibbs–Thomson effect. Qualitative reproduction of the reported observation showed that the effective surface free energy of SiC during CVD can be doubled by the addition of HCl

Abstract: As the demand for sustainable environment friendly materials increases, the biocomposites such as wood-polymer composite (WPC) have gained more attention in past years. Wood wastes and by-products like sawdust, chips, bark and wood residues as well as recycled polymers can serve as raw materials for production of WPC. However, there are still many issues obtaining WPCs, mainly a poor compatibility between a hydrophobic polymer matrix and a hydrophilic wood filler. In the present study, mechanical and mechanochemical activation of aspen wood waste were performed to increase their compatibility with recycled polypropylene matrix in the WPC, and the impact of both methods on the biocomposite properties were studied. It was found, that mechanochemical activation (MCA) of aspen wood particles leads to increased hydrophobicity of the obtained WPC compared to the WPC with mechanically activated (MA) particles. Work of adhesion with water was remarkably lower for the WPC modified by MCA which also correlates with moisture sorption results. Surface free energy of the WPC modified by MCA was lower compared to the WPC modified by MA, mostly due to decreased the polar component of surface free energy. The modulus of elasticity (MOE) were competitive for both the WPC formulations, however, MCA led to increased flexural strength of WPC compared to MA.

Abstract: In this study, hydrophobic-hydrophilic characteristics, including contact angle and moisture sorption of a modified wood filler and the wood-polymer composites (WPC) containing it was investigated. The wood filler obtained from aspen sawdust was modified by mild acid hydrolysis and by ammoxidation. Contact angles of the wood particles and the WPC samples were measured with Kruss K100M using the Washburn and Wilhelmy methods, respectively. Work of adhesion was calculated using Young-Dupre equation. Surface free energy as well as its dispersive and polar parts were found using Owens-Wendt-Rabel-Kaelble approach. It was found that the hydrolysis and the ammoxidation led to decrease of the hemicelluloses content in the lignocellulosic matrix. Beside this, the ammoxidation favours the formation of amide bonds in the ammoxidised particles. These changes enhanced the contact angles, decreased the work of adhesion, and decreased surface free energy of the WPC samples filled with the modified particles in comparison with the WPC sample that contained the unmodified ones. The treatment of the wood particles decreased the wettability towards water, but increased it towards recycled polypropylene. This positively effects mechanical properties of the samples.

Abstract: The aim of the study was to evaluate the surface energetic characteristics of wood-polymer composites (WPCs) based on recycled polypropylene (rPP) filled with ammoxidised lignocellulosic microparticles, obtained from aspen sawdust, a by-product of a Latvian company. The aspen sawdust, pre-hydrolysed in acidic medium, was treated with a reaction mixture of ammonium persulphate and NH₄OH solution at their defined mass ratio during 120 h. The content of the introduced nitrogen was varied from 1,05 to 2,10%. It was found that the ammoxidation that was accompanied with the formation of amide linkages and the decrease of the hemicelluloses content enhanced the contact angles, decreased the work of adhesion and reduced the surface free energy of the WPC samples in comparison with the case of the composite filled with the initial sawdust. The valorisation of the wood particles increased their wettability towards the recycled polypropylene that had a positive effect on the WPC samples’ mechanical properties.

Abstract: In this study there was compared the effect of different methods of modification (modification by plasma treatment and ionizing beta radiation) on the surface properties (contact angle of wetting and surface free energy) and on the final strength of bonded joints of selected types thermoplastics (low density polyethylene and polycarbonate). At the present time bonding has spread into almost all sectors of practice and it would be very difficult to find an industry in which there is no need to use this technology of joining a wide range of materials. Generally, for the formation of quality bonded joint it is important to wet the adhesive bonding surface well. Wettability is characterized by the contact angle of wetting. The liquid has to have a lower surface energy than the solid in order to be able to wet the solid substance.

Abstract: Recently the laser beam treatment is more and more in common practice. The fields of use are very diverse. One of these fields of activity is removing of pollutions from a surface and preparation of it before the next stage of treatment. In the paper are presented the results of experimental research which were conducted in the aim of assessment of effects after cleaning of AISI 4130 steel by laser beam. The indicator of process quality was surface free energy (SFE) which is well known indicator in the operation where adhesion is very important. To its assess the measurement of wettability angle is required. After the experiment the results show that it is possible to improve the energetic state of the surface, thus the better preparing of surface before activity when the good adhesion properties are needed than in the case of traditional manner of treatment.